issue after changing the color of the UV image with photoshop
On your 3rd image you can see that on each polygon border on your UV layout the color are brighter, this probably happened in Photoshop for some reasons. This is what causing the wireframe pattern on your last image.

To do the same thing in the node editor you should use a Color Ramp node, which will convert your RGB image to a grayscale image. Then you can control your skin color with a RGB node.